1. FIELD OF THE INVENTION
The present invention relates to a method of measuring and displaying double refraction occurring in a material to be measured, which makes it possible to obtain the data on molecular orientation of the molecular chain in the material by determining the double refraction and the double refraction fast axis in the same.
2. DESCRIPTION OF THE PRIOR ART
In almost all of the materials such as calcite capable of transmitting light in which crystals or molecular chains are arranged, light which has entered the material becomes two refracted light rays, i.e., is subjected to double refraction. There has in recent years been a demand for a double refraction measuring technique which is intended to measure, by utilizing such double refraction, the fast axis, i.e., molecular chain axis deviation having occurred, in a high polymeric material.
A conventional apparatus for measuring double refraction occurring in a material to be measured is constructed as shown in FIG. 7. Measuring light 100 is prepared by causing light emitted from a light source 101 to be circularly polarized by passing it through a polarizer 102 and a quarter wave plate 103. A conventional method of measuring double refraction occurring in the material consisted in causing the measuring light 100 to be passed through a fixed material specimen 104, detecting the resulting measuring light 100 by means of a photodetector 106 such as a photomultiplier after passing it through an analyzer 105 arranged to rotate at approximately 30 rotations per second, and performing a Fourier analysis or the detected signal to determine the ellipticity of the measuring light, thus to determine the maximal value and its plus or minus sign of the double refraction.
With the above-mentioned conventional double-refraction measuring method, however, it was entirely impossible to obtain, from such a maximum value or a sign of double refraction, information on molecular orientation, i.e., information concerning in what direction an orientation angle of the main axis of a molecular chain or a plus or minus sign corresponds on a measured specimen. When a discussion is made on the molecular chain axis deviations involved in a high-polymeric substrate material such as an optical memory storage disk, it has recently been inevitably necessary to obtain such data on molecular orientation. Thus, the absence of any prior art technique serving such purpose has become a great problem.